1. Field of Invention
The invention relates to a nozzle system for a delivery device for liquids which comprises a nozzle and a device which fixes the nozzle in the delivery device. The device has a liquid reservoir from which a liquid is forced through a nozzle under pressure to deliver the liquid. The nozzle is secured by a holder on the delivery device. This holder may itself be secured by a second holder, e.g. in the form of a check nut, or the check nut itself may be the holder. According to the invention at least part of the outer surface of the holding device is micro- or nanostructured.
Preferably, the present invention is part of a propellant-free device for nebulising pharmaceutical fluids. A nebuliser according to the invention is used, for example, to produce an aerosol of droplets for inhalation through the mouth and pharyngeal cavity into the lungs of a patient, for nasal administration or for spraying the surface of the eye.
2. Related Prior Art
WO 91/14468 discloses an apparatus for propellant-free administration of a metered quantity of a liquid pharmaceutical for application by inhalation. A further development of the device is described in detail in WO 97/12687. Reference is specifically made to these publications and the technology described therein is referred to within the scope of the present invention as RESPIMAT® technology. This term refers in particular to the technology which forms the basis for a device according to FIGS. 6a and 6b of WO 97/12687 and the associated description.
In an inhaler of this kind liquid pharmaceutical formulations are stored in a reservoir. From there, they are conveyed through a riser tube into a pressure chamber from where they are forced through a nozzle. The nozzle has a liquid inlet side and a liquid outlet side. On the liquid inlet side is an opening through which a liquid from the pressure chamber can enter the nozzle. On the opposite side, the end face of the nozzle, the liquid then passes through two nozzle apertures which are aligned so that the jets of liquid leaving the apertures strike one another and are thereby atomised. The nozzle apertures are arranged in the inhaler in such a way that they are in direct contact with the outer environment. These inhalers normally deliver formulations based on water or mixtures of water and ethanol. They are able to nebulise a small amount of a liquid formulation in the therapeutically required dosage within a few seconds to produce an aerosol suitable for therapeutic inhalation. With the device, quantities of less than 100 microlitres can be nebulised, e.g. with one spray actuation, to produce an aerosol with an average particle size of less than 20 microns so that the inhalable part of the aerosol corresponds to the therapeutically effective amount. In these nebulisers with RESPIMAT® technology a pharmaceutical solution is converted by high pressure up to 500 bar into a low-speed aerosol mist destined for the lungs, which the patient can then breathe in.
A small amount of the liquid may be deposited from the outside as a film or as an accumulation of small droplets on the end face of the nozzle or on the end face of the fixing means for the nozzle or on the inside of the mouthpiece. This fraction of the liquid is also referred to as the mouthpiece fraction within the scope of this specification.
The amount of liquid deposited need not be constant in every spray actuation but may depend on numerous factors such as the spatial orientation of the device during the aerosol production or the ambient temperature, relative humidity, etc. This leads on the one hand to a certain variability, however minor, in the amount dispensed which is then available for the patient to take in. The liquid deposited may also cause contamination of the outer surface of the nozzle system or of the mouthpiece, which may in turn affect the pharmaceutical quality of the next aerosol mist.
Although these two effects are only slight in devices using RESPIMAT® technology it is important for reasons of quality control to minimise such effects.
It has now surprisingly been found that in devices for dispensing liquids the proportion of liquid deposited on the outside of the nozzle system can be reduced if the corresponding surfaces are at least partially micro- or nanostructured. Devices based on the RESPIMAT® technology are preferred.